A reference terminal is, for example, an analog telephone connected to, for example, a circuit-switched telephone network or an ISDN (Integrated Services Digital Network) telephone. However, this technology also relates to terminals that are connected to a packet-transmitting data transmission network, e.g., computers that are connected to the Internet. The terminals serve for the transmission of digital voice data, for example. However, other data can also be transmitted, for example video data, depending on the structure of the terminal.
Features or services supplement pure transmission services and make their use more user-friendly. For example, there are the following features for the ISDN, particularly the Euro-ISDN:                call waiting (Dial Call Waiting),        automatic call-back if a line is “busy” (Call Completion Supplementary Service),        conference calls,        holding a connection.        
Similar features are also being slowly established for packet-transmitting data transmission networks, for example, by the ITU-T (International Telecommunication Union—Telecommunication Standardization Sector) or the IETF (Internet Engineering Task Force).
The operating state of the terminal characterizes the current mode of operation if, for example, the terminal is just transmitting data or it is in a waiting state in which it is not busy. In addition to the “busy” or “engaged” state and the “not busy” state, there is a multitude of other operating states of the terminal, for example the “not answering” operating state, in which a subscriber using the terminal or an operator is called using a signaling device, but does not go to the terminal to operate it.
Until now, the features for processing requests in different operating states of the terminal were established from the reference terminal end. The selection established was stored in memory for the reference terminal. Each subscriber could therefore select features only for himself/herself. For example, a subscriber could select from two options for the “busy” operating state with a reference terminal, namely whether he/she wishes to select the “call back if busy” (CCSB) feature or the “call waiting” feature. A prerequisite in this connection was that these features had also been activated for the subscriber in question by the network operator, usually in return for payment of a fee. To date, other selection possibilities have been created, for example for features that relate to the “no answer” operating state. In this case, call forwarding to an answering machine or to another connection is possible, for example. The selection possibilities available to date are being extensively utilized by a large number of subscribers and/or users.